Ok, this isn't intuitive at all, but I've got to tell you that watching calories might not be the enitre story...so be careful.
I'm in my INSANITY recovery week this week. I'm also doing doubles two days a week where I do a P90X upper body workout (evenings) along with my Insanity workout (early mornings). I was getting a little frustrated because in my first 3 weeks of Insanity I lost a total of 3 lbs. I also lost 3/4" off my waist and 4" total in body measurement...and added 1/4" to my biceps but after getting great results with P90X I was really expecting a lot more from the Insanity.
I have been watching what I eat very carefully logging all my meals and keeping my splits at 40/40/20 (protein/carbs/fat) or at least as close as I can get. I figured in no time I'd drop the lbs I gained at the end of last year and be in tip top shape. According to my food log I was averaging anywhere from 1600 - 1900 calories per day. Actually quite a bit of food if you're eating good food but losing no weight.
I went back through some of my Beachbody newsletters and also talked to our nutritionist at work and they both had the same advice...I had to eat more. From what the nutritionist told me the body requires anywhere from 1200 - 1500 calories, depending on body type/size, just to perform normal functions. According to her, once you get below that level the body goes into "conservation" mode, in essence, it shuts down so you don't starve yourself. So if she's right, then my body has gone into conservation mode because my daily calorie intake, coupled with the exercise, was putting me below the minimum required calories for my body to function.
So last week I pushed myself to eat more, actually got up to ~ 2200 calories each day and I LOST 3 1/2 LBS!!! Go figure...It is a chore to eat 2200 good calories but I'm trying. Yesterday I had to eat two sirloin burgers (~ 9 oz) at dinner just to get to 2050 calories but that was a lean day. Today I'm back up to 2282 calories. If I could add a few twinkies, cakes or puddings I'd have no problem but eating good food it quite a bit different. I'm going to try to get up to 2500 calories but at this time it doesn't seem possible...we'll see... I'll keep you posted.